1. Field of the Invention
The present invention relates in general to DC converting apparatuses, and more particularly to an AC to DC converting apparatus not employing any multiplier for controlling a power factor.
2. Description of the Prior Art
FIG. 1 is a block diagram showing a conventional AC(Alternating Current) to DC(Direct Current) converting apparatus.
Referring to FIG. 1, the conventional AC to DC converting apparatus has a rectifying unit 10, a current sensing unit 30, a first adder 71, voltage controller 20, a multiplier 72, a second adder 73, current controller 40, PWM (Pulse Width Modulation) unit 50, and a switching device 60. The rectifying unit 10 rectifies an AC supply voltage. The current sensing unit 30 senses an output current from the rectifying unit 10, and the first adder 71 adds an output voltage Vdc to a reference voltage for controlling an output voltage Vdc. The voltage controller 20 performs a voltage control operation according to an output signal from the first adder 71. The multiplier 72 multiplies the output voltage from the voltage controller 20 by an output voltage from the rectifying unit 10 after adjusting the level of the voltage by a first level-adjusting unit 11. The second adder 73 adds the output signal from the multiplier 72 to an output signal from the current sensing unit 30 after the level of the signal is adjusted by a second level-adjusting unit 31. The current controller 40 performs a current control operation according to the output signal from the second adder 73. The PWM unit 50 generates a PWM signal in response to the output signal from the current controller 40. The switching device 60 switches the output voltage from the rectifying unit 10 to output the voltage Vdc. The multiplier 72, the second adder 73, the current controller 40, and the PWM unit 60 are integrated into a power factor control IC 80.
The AC to DC converting apparatus having the above construction takes an output voltage from the rectifying unit 10 as a rectified voltage for controlling a power factor. In order to obtain a phase of the rectified voltage, the AC to DC apparatus employs the multiplier 72, such that the multiplier 72 multiplies the output signal from the voltage controller 20 by the output voltage from the rectifying unit 10 after adjusting the level of the output voltage. Then, the current controller 40 generates a current following signal for current control. The second adder 73 adds the current following signal to the sensed output current from the current sensing unit 30 after adjusting the level of the output current, and the added signal is applied to the current controller 40.
Accordingly, the conventional AC to DC converting apparatus is problematic in that its manufacturing costs are increased due to an addition of a multiplier used for obtaining phase information for controlling a power factor. Further, the conventional apparatus controls an output current of a rectifying unit using a sine wave control method for power factor control, such that it has nonlinear characteristics, thus deteriorating its entire operating characteristics.
Therefore, the present invention has been made in view of the above problem, and it is an object of the present invention to provide an AC to DC converting apparatus, which does not employ any multiplier for controlling a power factor, and compensates for its non-linear components.
In accordance with one aspect of the present invention, the above and other objects can be accomplished by the provision of an AC to DC converting apparatus, comprising a